1. Field of the Invention
The present invention relates to a suspension control system for a suspension which suspends a wheel of a vehicle, wherein the suspension includes a damper having an actuator for changing a damping force of the damper.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2002-211224 discloses a suspension control method wherein the spring rate of a coil spring used by a suspension is changed by an actuator-generated torque according to the steering angle speed of a steering wheel and the rolling angle of a vehicle. Accordingly, any increase in the rolling angle due to the vehicle turning is suppressed, thereby improving running stability.
However, in the method described in Japanese Patent Application Laid-open No. 2002-211224, the rolling angle of the vehicle is detected from an output of a displacement sensor disposed in the suspension, and the actuator is controlled wherein the detected rolling angle is identical to a predetermined target value. That is, the actuator is controlled to suppress the rolling after an actual rolling of the vehicle occurs. As such, the control response is delayed, which results in a deterioration of riding comfort during control of the rolling angle.
Also, Japanese Patent Application Laid-open No. 2000-148208 discloses a suspension control system in which the control is switched between a riding comfort control and a posture control by, for example, monitoring a steering angle signal. During riding comfort control, the damping force of a damper is controlled to suppress vibrations transmitted from a road surface to the vehicle body via a suspension. During posture control, the damping force of a damper is controlled to improve running stability by suppressing the change of a rolling angle resulting from the turning of the vehicle or suppressing the change of a pitch angle resulting from the acceleration and deceleration of the vehicle.
However, in the system described in Japanese Patent Application Laid-open No. 2000-148208, the riding comfort control for improving riding comfort of the vehicle and the posture control for improving running stability of the vehicle are selectively performed based on the driving condition of the vehicle. Accordingly, the damping force of the damper suddenly changes during the control switch-over, thereby resulting in a rough or not-smooth driving experience for the driver which can be rather uncomfortable.